The present invention generally relates to a vehicle body conveyance in an assembly line and, more particularly, to a conveyor assembly that extends through a door fitting station.
As is well known to those skilled in the art, an automobile assembly line includes a number of work stations at which different assembling operations are generally simultaneously performed to automobile body structures being successively conveyed. Among the other work stations, these work stations include a door fitting station where door assemblies are fitted from both sides to an automobile body structure being moved on a conveyor. The conveyor that extends through the door fitting station is generally employed in the form of a so-called slat conveyor similar in appearance to a caterpillar or crawler track. Briefly speaking, the slat conveyor comprises a belt of slats articulately connected together in side-by-side relationship with respect to each other and driven to travel from one place to another and then back to the one place. In any event, the structure and the operation of the slat conveyor are well known in the art.
When it comes to an automatic door fitting, Japanese Laid-open Patent Publication No. 52-34480, published Mar. 16, 1977, discloses the installation of an accompanying carriage on both sides of a vehicle body transporting conveyor at the door fitting station, and a hydraulically driven door fitting assembly operatively mounted on the carriage. The door fitting assembly on each side of the conveyor includes a cylinder for driving an arm between retracted and fitting positions in a direction perpendicular to the direction of run of the conveyor, one end of the arm remote from the cylinder having a hingedly supported suction cup assembly for the support of a door assembly to be fitted to the automobile body structure. The carriage has a motor-driven, telescopically movable connecting rod adapted to engage a portion of the automobile body structure when the latter being conveyed is brought to a predetermined position, so that the carriage can be pulled forward to the accompaniment of the forward run of the automobile body structure. During the movement of the carriage accompanying the automobile body structure, the cylinder is actuated to fit the door assembly to the body structure in a manner controlled by a remote control unit, and accordingly, what the attendant worker or workers have to do at the door fitting station is to install hinge pins to connect the door assembly hingedly with the body structure.
The connecting rod is held in a retracted position when and so long as the body structure has not yet been brought to the predetermined position.
The conveyor used in this publication is described as a floor conveyor, and no other details thereof are disclosed therein because of the nature of the invention directed essentially to the automatic door fitting system.
When the automatic door fitting system such as disclosed in, for example, the above mentioned publication is employed in the automobile assembly line, the most important problem is how to exactly align the door assembly to be fitted with an associated door fitting opening in the body structure. While this exact alignment is considered relatively easy to achieve where the body structure is of a self-supporting or unitized type because the self-supporting or unitized body structure although having no conventional framework such as a chassis is reinforced in itself, the body structure of a type that requires the use of the conventional framework, such as a chassis-mounted vehicle body, for example, a cab structure for a truck or tractor, is susceptible to the misalignment because of the reason which will now be described with particular reference to FIG. 1 of the accompanying drawings.
In FIG. 1, the cab structure A for, for example, a truck is shown as mounted on the slat conveyor B through leading and trailing pairs of shim members C, the leading pair of the shim members C being positioned between the rearmost portion of the cab structure A and the slat conveyor B whereas the trailing pair of the shim members C are positioned between the foremost portion of the cab structure A and the slat conveyor B with the leading and trailing pairs of the shim members spaced a substantial distance from each other. Because of the reason described hereinbefore, the cab structure A has a smaller rigidity than the self-supporting or unitized body structure and, therefore, during the transportation on the assembly line while mounted on the slat conveyor B as shown, an intermediate portion of the cab structure A between the rearmost and foremost portions thereof tends to droop under its own weight as shown by the phantom line. As a matter of course, once this drooping occurs, the shape of the door fitting opening on each side of the cab structure is deformed to such an extent as to deviate from the mating shape of the door assembly to be fitted thereto and, therefore, the hinge brackets rigid or integral with the door assembly may fail to align with associated hinge members A' rigid with a respective front side pillar of the cab structure A and with which the hinge brackets are to be connected by means of respective hinge pins.
Considering that the installation of the hinge pins is performed while the door assembly is in an opened position relative to the cab structure A, the hinge brackets rigid or integral with the door assembly may be successfully connected with the respective hinge members even though the door assembly as a whole does not exactly align with the door fitting opening. However, where the hinge brackets are connected with the hinge members in this way, and when the cab structure with the door assemblies installed thereon is subsequently mounted on a chassis at the subsequent work station with the drooping phenomenon consequently removed, the door assemblies will require a readjustment to permit them to be selectively opened and closed smoothly relative to the cab structure A.